While rising fast food consumption has been considered to be the major factor causing rapid increases in childhood obesity for years, researchers said fast food consumption is simply a byproduct of a much bigger problem: poor all-day-long dietary habits that originate in children's homes.

Researchers at The University of North Carolina at Chapel Hill found that children's consumption of fast food is only a small part of a much more pervasive dietary pattern that is fostered at an early age by children's parents and caregivers.

The pattern includes few fruits and vegetables, relying instead on high amounts of processed food and sugar-sweetened beverages. These food choices also are reinforced in the meals students are offered at school.

"This is really what is driving children's obesity," said Barry Popkin at UNC's Gillings School of Global Public Health, whose team led the study.

"Eating fast foods is just one behaviour that results from those bad habits. Just because children who eat more fast food are the most likely to become obese does not prove that calories from fast foods bear the brunt of the blame," Popkin said.

The study examined data acquired through the National Health and Nutrition Examination Survey (NHANES) between 2007 and 2010.

Dietary intake, including whether foods and beverages were obtained in fast-food establishments or elsewhere, was evaluated in 4,466 children who were 2 years to 18 years of age.

They were further categorised as being non-consumers of fast food (50 percent of the children), low consumers (less than or equal to 30 per cent of calories from fast foods; 40 per cent of the children) or high consumers (more than 30 percent of calories from fast foods; 10 percent of the children).

The researchers then determined which factors were most related to dietary adequacy and risk for obesity.

"The study presented strong evidence that the children's diet beyond fast-food consumption is more strongly linked to poor nutrition and obesity," said Jennifer Poti, doctoral candidate in UNC's Department of Nutrition and co-author of the study.

"While reducing fast-food intake is important, the rest of a child's diet should not be overlooked," Poti said.

"Children who rely on fast foods may tend to have parents who do not have the means, desire or time to purchase or prepare healthy foods at home," Popkin said.